I don't know what you expect, even if there were "advanced tactics" low health enemies would still die too fast to matter, what would the point be of creating advanced tactics if the enemies die too fast to actually use them.
The "bullet sponges" last long enough to actually achieve things against you when you are powerful, exactly as their weaker brethren should when you are weak.
"Oh no those low level super mutants are flanking me while the ones in front provided covering fire, a suicider is rushing me, and that one is going for that dropped rocket launcher, BRRRRRRRRRRRRRRRRRRRT(fired while spinning 360), few they are all dead because I'm ungodly powerful and they have next to no health"
Tactics require time, melee enemies rushing you while ranged ones provide support does not work when you can kill the ranged ones first, then kill the melee ones as well before they get to you. The only way to buy time against the pc is to either preform some ridiculous crowd control to take away their ability to react (aka, stunlock bs that everyone hates), force them to use slow tactics that prevent them from reacting (aka, enemies shoot you dead instantly), or make the enemies tough so the reaction happens at a slower rate (durable enemies).
You either make the enemies so lethal you can't survive, or make the enemies so tough that they can. That warlord you are pumping bullets into is buying time for other mutants to run around behind you, get to cover, and close to melee range, he is suppressing fire and keeping you distracted, if he died instantly that would never have a chance to happen.
I have been smacked in the back because I was to preoccupied with one tough enemy, but if he died instantly I wouldn't have been.
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edit.
Suppressing fire is in the game, I don't know how to say this but all fire is suppressing fire, whether or not you are suppressed is a matter of whether you think it will kill you, a mutant firing a minigun at you and forcing you to duck behind a wall is suppressing fire.
Cover and flanking do also exist in game, but they are a matter of terrain coding, the ai is blind, they can not "see" cover, they can only react to what cover boxes have been programed as a part of the terrain, and they are completely at the mercy of the player's vision and the map developers code.